Different Page Layout for a Custom Theme

I’m learning how to design my own theme, and it’s a lot harder than I thought. I’m working on converting my existing site into a WordPress site. You can see the test site at https://beta.mrtechnique.com. I coded the index.php to include dynamic sidebars. I want to create another page layout which has no sidebars, just one big content area like at this url on my site:

https://www.mrtechnique.com/about-us.php

Any help would be appreciated. Thank you.